Negative reagent controls in diagnostic immunohistochemistry: do we need them? An evidence-based recommendation for laboratories throughout the world

During the development and application of immunohistochemical techniques to diagnostic pathology, controls have played an important role in ensuring that the appropriate result has been obtainted.The positive control is a tissue or collection of cells that contains the target protein (antigen) and confirms that the primary antiboby and detection system have worked properly. The negative control,used primarily for primary antiboby validation,is a specimen that does not contain the target protein and,as a result,should show no immunoreactivity. The negative reagent control(NRC) is an additional tissue section(frozen or paraffin) or cytology smear prepared from the patient specimen that is treated identically to that of the test slide(s) except for the omission of the primary antibody.Its primary purpose is to identify nonspecific reactivity due to factors or components other than the primary antibody.